Plastic glazing, in particular for motor car and method for making same

ABSTRACT

The invention relates to a product which is at least partly transparent and of high optical quality, equivalent to that of a glass window, which can be approved as a motor-vehicle window according to the various standards in force, and having a plastic core coated with a skin comprising at least one plastic film coated with a scratch-resistant layer; it also relates to a process for manufacturing this product and to the application of the latter as a body element, part of which forms a window, for example for motor vehicles.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to at least partly transparent productsmade of plastic, especially products of high optical quality, equivalentto that of a glass window. It is conceivable to replace glass sheetswith plastic sheets in the construction of windows, for example forbuildings or transport vehicles.

2. Description of the Background

Compared with glass, plastics are lower in weight, which is a keyadvantage in the case of electrically driven town vehicles, in so far asan increase in their range is crucial. In such vehicles, it could evenbe envisaged producing, from plastic, in a single unit, entire doors oreven complete sides of the body, including the windows, and, optionally,painting a lower part thereof. In general, the low weight of thetransparent surfaces is relatively advantageous in the case of moderntransport vehicles in so far as technical progress is going hand in handwith integration into windows of still more numerous functions (heatedrear window, radio antenna, windscreen de-icing, colouration in order toprevent the passenger compartment heating up in strong sunlight,incorporation of electrochromic compounds, display of information on thewindscreen, etc.) and with ever increasing amounts of glazed surfaces.This results in a general increase in the vehicle weight, to thedetriment of its energy consumption.

Moreover, compared with glass, plastics are capable of providingimproved safety conditions and superior anti-theft protection because oftheir greater toughness.

A not insignificant advantage of plastics compared with glass resides intheir superior ability to be easily converted into complex shapes.

Finally, the ability of plastic sheets to be deformed substantiallyreversibly makes it possible to envisage ways of fitting them intoconsiderably simplified body openings by a snap-fastening mechanism,from the inside just as from the outside of the vehicle.

According to a first approach, flat plastic sheets are formed byextrusion, a component is cut to the required dimensions and fastened toa thermoforming device, a contact thermoforming operation is carried outwith at least one solid mould surface and, optionally, with the aid ofcompressed air or suction. The optical properties of a sheet thusextruded are not satisfactory.

Furthermore, the scratchability of plastics, mentioned previously, issuch that, in their optical applications or as transparent elements, itis necessary to coat the shaped components with a hard varnish. Thisoperation is accompanied, as is well known to those skilled in the art,by problems of the varnish flaking, these problems being more acute inthe case of surfaces of complex shapes. In addition, it has only beenenvisaged forming the hard varnish at a temperature below thedeformation temperature or softening point of the plastic, the shape ofwhich is thus entirely preserved during this operation. Such conditionsof forming the varnish are excessively restrictive and have resulted inconsiderable effort being expended to produce varnishes which form atsufficiently low temperatures and, at the same time, thermoplastics withhigh softening points. There therefore remained the need for a plasticwhich is transparent or intended for optical applications, in which thepoor optical quality inherent in the extrusion technique and the problemof the varnish flaking would be avoided and in which many varnishescould be employed in combination with many plastics under satisfactorycomparability conditions.

This product should be capable of being obtained by an inexpensive,reliable and simple process.

SUMMARY OF THE INVENTION

These objectives are presently achieved by the invention, the subject ofwhich is a product which is at least partly transparent and of highoptical quality. More particularly, the invention resides in the factthat this product comprises a plastic core integral with a skincomprising at least one plastic film supporting a scratch-resistantlayer.

This is because the property by which the scratch-resistant layer issupported on a plastic film guarantees easy and reliable procurement ofan end-product of lasting high optical quality, as will become apparentin the rest of the description. It makes it possible to produce such anend-product on the basis of the scratch-resistant layer on its supportfilm in a physical and chemical state which will not be modifiedconsequently, or only very slightly, by combining it with the coreespecially by injection moulding the plastic of which it is composed.The use of certain scratch-resistant varnishes forming at relativelyhigh temperatures optionally requires choosing a material for thesupport film which is sophisticated but in a low quantity.

DETAILED DESCRIPTION OF THE PREFERRED INVENTION

The expression “high optical quality or optical quality equivalent tothat of a window” is understood to mean, in the sense of the invention,“optical quality equivalent to that of a glass window, which can beapproved as a motor-vehicle window according to the various standards inforce, especially the R 43 standard in use in France”.

Whatever the material of the core, the injection-moulding temperaturesshould not, of course, affect the other constituents of the product.This material may be chosen from many plastics; it may be a conventionalinexpensive thermoplastic having a relatively low softening point.According to the invention, the plastic of the core is capable ofinteracting with the skin for the purpose of obtaining high opticalquality, while at the same time having the desired mechanicalproperties, in particular flexural strength and impact strength.

Preferably, the skin has a thickness at most equal to 500 μm,particularly preferably between 10 and 100 μm, and comprises one or moretransparent thermoformable plastic films, for example made ofpolycarbonate (PC), polypropylene (PP), poly(methyl methacrylate)(PMMA), an ethylene/vinyl acetate copolymer (EVA), poly(ethyleneterephthalate) (PET), polyurethane (PU), polyvinyl butyral (PVB) or acycloolefin copolymer (COC), i.e. an ethylene/norbornene copolymer or anethylene/cyclopentadiene copolymer. One or more functions may beassigned to some of these thermoformable plastic films by theincorporation of suitable agents. Depending on its thickness and itsnature, the skin is capable of contributing to a greater or lesserextent to the mechanical properties of the product.

Moreover, a functional layer may be deposited on a thermoformableplastic film of the skin, this being, in particular, the case with thescratch-resistant layer. Finally, a functional layer may be sandwiched,autonomously, between two thermoformable plastic films.

Advantageously, the scratch-resistant layer has a thickness of between 1and 10 μm; generally, it forms the external surface of the product ofthe invention. It may essentially be inorganic and especially consist ofpolysiloxanes and/or of derivatives of silica and/or alumina, or ahybrid, such as consisting of networks of entangled inorganic andorganic molecular chains linked to each other by means of silicon-carbonbonds. Such a hybrid layer exhibits excellent transparency, adhesion andscratch-resistance properties. It appears that the inorganic networkgives the coating its hardness and its scratch resistance while theorganic network gives it its elasticity and its toughness. Suchvarnishes are well known and have been described in the publishedapplications EP-A1-0,524,417 and EP-A1-0,718,348, the teaching of whichis incorporated here by way of reference; some of these varnishes areespecially denoted by the registered trademark “Ormocer” which is anabbreviation for “Organically Modified Ceramic”. It is worth pointingout that the firing temperature of Ormocers is easily adaptable byvarying the relative amounts of the organic polymer fraction and theinorganic fraction. With regard to the plastic of the support film, itmay be useful, or indeed necessary, to adapt its composition so as tomake it compatible with the method and temperature of deposition of thescratch-resistant layer.

Other functionalities may be incorporated into the skin.

According to one particular embodiment, the external layer of the skin,in contact with the environments contains a hydrophobic/oleophobic agentwhich therefore imparts this property to the external surface of theproduct. As hydrophobic/oleophobic agent, fluorinated polysilanes arewell known, especially those obtained from precursors having ahydrolysable alkoxy- or halogeno-type functional group at one end, thisfunctional group serving for chemical bonding to the substrate, and aperfluorinated carbon chain at the other end, this chain being intendedto constitute the external surface of the product.

The hydrophobic/oleophobic agent is, in decreasing order of preference,incorporated into the scratch-resistant layer, which has a chemicalstructure close to its own, or with which it is at the very leastchemically compatible, or grafted in the form of a thin layer having athickness of between 2 and 50 nm, preferably onto the scratch-resistantlayer, or alternatively self-supported on a plastic film, such as apoly(vinyl fluoride) (PVF) or a poly(vinylidene fluoride) (PVDF), to beadvantageously applied directly to the scratch-resistant layer.

According to a variant, at least one decorative and/or masking layer,covering all or part of the surface of the product, is positioned in theskin, preferably directly under the support film of thescratch-resistant layer.

This layer may, for example, replace the screen-printed decoration oftendeposited around the periphery of the internal face of windows,especially for motor vehicles, for the purpose of masking, in the caseof an observer outside the vehicle, the body elements forming the frameof the opening and the adhesive bead which is thus protected fromdegradation by ultraviolet radiation. This layer may include opaque ortransparent coloured decorative elements, making it possible to producecoloured elements matching the body or the internal fittings, logos,etc.

The skin may be provided with an adhesion layer, in particular on itsinternal face for fastening to the core, but also between two films orlayers of the skin. Standard adhesives are polyvinyl butyral orpolyurethane.

Finally, among the main constituents of the skin are the opticallyselective layers which are stacked, for example beneath the decorativeand/or masking layer. These layers are distinguished by a hightransmission in the visible range (wavelengths from 400 to 800 nm) and ahigh absorption and/or reflection in the ultraviolet range (<400 nm) andinfrared range (>800 nm). These layers may consist of thin metal layers,for example based on silver, having thicknesses of between 2 and 35 nm,separated from each other, as well as from other adjacent layers orfilms, by dielectric layers of oxides or nitrides of indium, tin,silicon, zinc, titanium, tungsten, tantalum, niobium, aluminium,zirconium, etc., generally having thicknesses of between 10 and 150 nm.These layers may include at least one bulk-coloured layer.

The combination of these layers may be electrically conductive; it maybelong to the family of solar-protection stacks used for limiting theinflux of heat by solar radiation into closed spaces or to that oflow-emissivity stacks used, on the contrary, to limit the loss of heatfrom closed spaces, this loss being mainly due to transmission ofinfrared radiation through the window. Such stacks are described inPatents FR 2,708,926 and EP 0,678,484.

The core of the product of the invention consists of a thermoplasticsuch as polycarbonate, poly(methyl methacrylate), an ethylene/vinylacetate copolymer, poly(ethylene terephthalate), a cycloolefin copolymer(for example, an ethylene/norbornene or ethylene/cyclopentadienecopolymer), or of an ionomer resin (an ethylene/methacrylic acidcopolymer or an ethylene/acrylic acid copolymer neutralized with apolyamine, etc.), or of a thermosetting or thermally crosslinkablematerial (polyurethane, unsaturated polyester, ethylene/vinyl acetatecopolymer), or else of a combination of several thicknesses of the sameone or several of these plastics, on condition that the core ischemically compatible with the skin of the product according to theinvention and gives the assembly the required mechanical properties.

The subject of the invention is also a process for manufacturing theproduct described above.

In a first phase of this process, the constituents of the skin areassembled, this being in the form of a ply or developed, optionallyplane.

The scratch-resistant layer, when it is made of polysiloxanes, isadvantageously formed cold on its support film and/or by plasma-enhanceddeposition, such as plasma CVD (Chemical Vapour Deposition). Insofar aspolysiloxanes formed in this way are no longer reactive, having alreadycompletely reacted, it is necessary to choose the composition of thescratch-resistant layer so that it can be bent, in order to avoidsubsequent flaking problems.

When the scratch-resistant layer consists of Ormocers, these are appliedflat in the form of liquid precursors to the support film, using theconventional techniques of flow coating, dip coating, especially in abath of small volume for the sake of economizing, liquid spraying orcurtain spraying. The precursor consists, for example, of colloidaldispersions in solvents of several hybrid compounds, that is to saycompounds which are both organic and inorganic, or oflow-molecular-weight polymers functionalized by SiOR groups in a mixturewith tetraethoxysilane. The scratch-resistant layer is then cured usinga sol-gel process in which the precursor is firstly dried, passingthrough the intermediate state of a gel, by moderate radiation orheating, especially, in the latter case, at less than 50° C. The supportfilm is then always held substantially flat; the curing of the Ormoceris completed during the second phase of the process, described below,which consists in thermoforming the said skin by ultraviolet radiationand/or heating to temperatures of 100 to 300° C., and more specifically140–240° C.

In either case, the layers, in particular the scratch-resistant layer onthe assembled and bent end-product, meet the required properties for itsuse, especially the regulation optical properties when it is to be usedas glazing or as an element comprising a window for a transport vehicle,especially a motor vehicle.

The often complex shapes of motor-vehicle windows mean that thescratch-resistant layer in particular must be able to be bent withoutflaking and without cracking. Thus, advantageously, thescratch-resistant layer is only fully cured after its support has beenshaped and, preferably, it only starts to cure and crosslink at the sametime as its support is being shaped, so as finally to have a surfaceappearance without crazing or flaking.

The deposition and formation techniques which have just been describedmay also be used for incorporating the hydrophobic/oleophobic function,whether the corresponding agent forms an integral part of thescratch-resistant layer or is supported on a plastic film; when it isgrafted on as a thin layer, it is also preferably formed by depositingit in liquid form by spraying, if it consists of silanes, or byevaporation using techniques such as plasma CVD, optionally undervacuum.

The decorative and masking layer or layers are provided on supportfilms, especially made of plastic, according to the techniques used inprinting: screen printing, flexography, ink-jet printing, laserprinting, etc.

The adhesion layer is usually provided in the form of an integralthermoplastic film.

The formation of optically selective stacks makes use of successivedeposition operations using sputtering, especially sputtering assistedby a magnetic field, or the like. In this regard, reference may again bemade to Patents FR 2,708,926 and EP 0,678,484.

The first phase of the process of the invention for forming thesubstantially flat skin may be concluded by an operation whose purposeis to consolidate the constituents thereof to a greater or lesserextent, especially by cold calendering or calendering at a temperatureslightly above room temperature.

As briefly mentioned above, the second phase of the process consists inthermoforming the skin at a preferred temperature of 100–300° C. into ashape, optionally non-developable, identical to that of the end-product.

To do this, it is advantageous, in particular in order to complete thecuring and/or crosslinking of the scratch-resistant layer, to allow itto come into contact with the ambient atmosphere, that is to say withoutcoming into contact with solid elements; only the other face of the skinis then in contact with a support whose purpose is to give it shape.Auxiliary means, for example, blowing or suction means, may be used toshape at least part of the skin to this support. Apart from completingthe crosslinking of certain constituents, the heat treatment carried outin this second phase has the effect of relaxing the stresses in theskin.

The third phase of the process of the invention consists in joining theskin to a plastic core by hot pressing in a form or by thermoplasticinjection moulding or reactive injection moulding (RIM) of the materialof the core, the skin having been positioned in the bottom of the mould,at the start of this third phase, in such a way that itsscratch-resistant layer and/or its hydrophobic/oleophobic layer, whichlayer is fully cured and/or crosslinked, i.e. virtually no longerreactive, is in direct contact with the mould wall.

Another object of the invention is the application of the productdescribed above as a body element, a transparent part of which forms awindow, especially for motor vehicles.

The invention will now be illustrated by the following example.

EXAMPLE

The scratch-resistant coating described in the example in PatentApplication EP-A-0, 718, 348 is deposited as a 20 μm thick liquid filmon an 80 μm thick film of standard polycarbonate prepared from bisphenolA, sold by Bayer AG under the registered trademark “Makrolon®”, whichhas a glass transition temperature Tg equal to 145° C., by flow coating.

Upon drying, this thickness is reduced to 5 μm.

The coated support film is then placed in the bottom of a mould, thescratch-resistant layer being positioned on top; the assembly is thensubjected to a heat treatment of 155° C. for 30 min. A skin in the senseof the present invention is then formed, this having its virtually finalshape.

The skin is placed in the bottom of an injection mould so that thescratch-resistant layer is in contact with the mould wall. There thenfollows, in the manner described above, the thermoplastic injectionmoulding, on two different specimens, of a 5 mm thick layer, on the onehand, and a 10 mm thick layer, on the other hand, of the same standardpolycarbonate as that making up the support film of thescratch-resistant layer.

The laminate obtained exhibits a transparency and an optical qualitywhich are amply sufficient for application as a window.

The process of the invention has the advantages inherent in theinjection-moulding technique. It is thus possible to form theinjection-moulded component with a peripheral bead in order to increaseits stiffness, or with a relief and/or extensions, such as ribs,profiles, tabs or lugs, and/or to arrange one or more inserts,especially metal inserts, in the plastic. This arrangement isparticularly useful for gripping or fastening the product of theinvention, as well as for fitting it in its intended final position,such as in a body opening of a motor vehicle. In the latter case,forming suitable peripheral profiles makes it possible to envisagefitting the product from inside the vehicle, i.e. from inside thepassenger compartment. The adhesive bead is then placed under the edgeof the body opening and is not exposed to solar radiation. Protectingthe adhesive bead with a varnish formed around the periphery of theinternal face of the sheet becomes, of course, superfluous.

The appendages formed around the periphery of the product while it isbeing injection moulded may be preserved, or sawn off completely orpartly depending on their use. After such sawing, a rubbing-downoperation may be provided.

A peripheral profile with a geometry which is symmetrical with respectto the plane of the product nay be opportune, for example in the case oftransparent side surfaces of transport vehicles, it being possible forone or other part of the profile to be subsequently sawn off, dependingon whether it is a left-hand or right-hand transparent element.

Moreover, optional inserts may be associated with the incorporation intothe product of special functions, such as a stop light in a rear window.

Finally, the process of the invention is economic, easy and reliable andallows the use of many combinations of constituents without the problemof their compatability, especially from the standpoint of theirprocessing temperatures, arising.

1. A glass-free motor vehicle window, which is at least partlytransparent, and which meets French standard R43 for motor vehiclewindows, which comprises: a.) a plastic layer having a thickness of 5 to10 mm, b.) at least one skin layer of a plastic film having a thicknessof 10 to 100 μm coated on said plastic layer, at least one adhesionlayer between said layer a.) and layer b.), and c.) a scratch-resistantlayer having a thickness of 1 to 10 μm supported by said plastic film,wherein said window is prepared by the following process (A) or process(B), wherein process (A) comprises: 1.) providing said skin layer b.),either flat or in shaped form, 2.) subjecting said skin layer to heattreatment, the skin layer, being supported completely or partly by amould surface, an auxiliary means for shaping at least part of the skinto the said mould surface being optionally provided so as to relaxstresses in the skin, and crosslinking constituent elements of thescratch resistant layer; and 3.) joining the skin to said plastic layera.) by hot pressing in a form, or by thermoplastic injection moulding orreactive injection moulding of the material of the plastic layer a.),the skin having been positioned in the bottom of the mould in such a waythat a scratch-resistant layer c.) is in direct contact with the mould;and process (B) comprises: 1.) depositing the constituent elements of ascratch-resistant layer on a substantially flat plastic film; and 2.)shaping said film bearing the elements of the scratch-resistant layerinto a shape which is the same as or at least similar to the ultimateshape of the end-product, while at the same time at least partlycrosslinking the scratch-resistant layer.
 2. The glass-free motorvehicle window according to claim 1, wherein said plastic layer a.)comprises a thermoplastic, comprising polycarbonate,poly(methylmethacrylate), an ethylene/vinyl acetate copolymer,poly(ethylene terephthalate), polyurethane or a cycloolefin copolymer,or an ionomer resin or a thermosetting or thermally crosslinkablematerial of a polyurethane, unsaturated polyester or ethylene/vinylacetate copolymer, or a combination of several thicknesses of the sameor several of these plastics.
 3. The glass-free motor vehicle windowaccording to claim 1, wherein said skin layer b.) comprises of one ormore transparent thermoformable plastic films made of polycarbonate,polypropylene, poly(methyl methacrylate), an ethylene/vinyl acetatecopolymer, poly(ethylene terephthalate), polyurethane, polyvinyl butyralor a cycloolefin copolymer.
 4. The glass-free motor vehicle windowaccording to claim 3, wherein interposed between plastic films (b.) ordeposited on said plastic film b), is at least one functional layer. 5.The glass-free motor vehicle window according to claim 1, wherein saidscratch-resistant layer c.) is inorganic, or consists essentially ofnetworks of entangled inorganic and organic molecular chains linked toeach other by silicon-carbon bonds.
 6. The glass-free motor vehiclewindow according to claim 5, wherein said inorganic scratch-resistantlayer c.) consists essentially of polysiloxanes, silica or alumina. 7.The glass-free motor vehicle window according to claim 1, wherein anexternal layer of said glass-free motor vehicle window comprises ahydrophobic/oleophobic agent which is incorporated into saidscratch-resistant layer c.), grafted onto said scratch-resistant layerc.), or self-supported on a film of poly(vinylfluoride) orpoly(vinylidene fluoride) applied directly to said scratch-resistantlayer c.).
 8. The glass-free motor vehicle window according to claim 7,wherein said hydrophilic/oleophilic agent is obtained from precursorsilanes having a hydrolyzable alkoxy- or halo-functional group at oneend and a perfluorinated carbon chain at the other end.
 9. Theglass-free automobile window according to claim 1, wherein said skinlayer b) includes at least one decorative or masking layer or bothcovering all or part of the surface of the window.
 10. The glass-freeautomobile window according to claim 1, wherein the skin layer b.)includes one or more optically selective layers, having thicknesses ofbetween 2 and 35 nm and separated from each other, as well as from otheradjacent layers or films, by dielectric layers.
 11. The glass-freeautomobile window according to claim 10, wherein said opticallyselective layers are metal layers.
 12. The glass-free automobile windowaccording to claim 1, wherein said scratch resistant layer c.) has asurface appearance without any crazing.
 13. A method of incorporating abody element, at least a portion of which is transparent, in amanufactured object, which comprises incorporating the glass-freeautomobile window according to claim 1, into an automobile.
 14. Aprocess for preparing a glass-free automobile window which is at leastpartly transparent, and which meets French standard R43 for motorvehicle windows, which comprises: a.) a plastic layer having a thicknessof 5 to 10 mm, b.) at least one skin layer of a plastic film having athickness of 10 to 100 μm coated on said plastic layer, at least oneadhesion layer between said layer a.) and layer b.), and c.) ascratch-resistant layer having a thickness of 1 to 10 μm supported bysaid plastic film, which process comprises: 1.) providing said skinlayer b.), either flat or in shaped form, 2.) subjecting said skin layerto heat treatment, the skin layer, being supported completely or partlyby a mould surface, an auxiliary means for shaping at least part of theskin to the said mould surface being optionally provided so as to relaxstresses in the skin, and crosslinking constituent elements of thescratch resistant layer; and 3.) joining the skin to said plastic layera.) by hot pressing in a form, or by thermoplastic injection moulding orreactive injection moulding of the material of the plastic layer a.),the skin having been positioned in the bottom of the mould in such a waythat a scratch-resistant layer c.) is in direct contact with the mould.15. The process of claim 14, wherein said constituent elements aresupplied by screen printing, flexography, ink jet printing, laserprinting, dip coating or spraying.
 16. The process of claim 14, whereinin step 2), said heat treatment is effected at 100° to 300° C.
 17. Aprocess for preparing a glass-free automobile window which is at leastpartly transparent, and which meets French standard R43 for motorvehicle windows, which comprises: a.) a plastic layer having a thicknessof 5 to 10 mm, b.) at least one skin layer of a plastic film having athickness of 10 to 100 μm coated on said plastic layer, at least oneadhesion layer between said layer a.) and layer b.), c.) ascratch-resistant layer having a thickness of 1 to 10 μm supported bysaid plastic film, which process comprises: 1.) depositing theconstituent elements of a scratch-resistant layer on a substantiallyflat plastic film; and 2.) shaping said film bearing the elements of thescratch-resistant layer into a shape which is the same as or at leastsimilar to the ultimate shape of the end-product, while at the same timeat least partly crosslinking the scratch-resistant layer.
 18. Theprocess of claim 17, wherein the crosslinking and simultaneous shapinginvolve a heat treatment at a temperature of from 100 and 300° C. 19.The process of claim 18, wherein the temperature is from 140 to 240° C.20. The process of claim 17, wherein the shaping is carried out bysupporting the film coated with the scratch-resistant layer, or theelements intended to constitute this layer, at least on part of itssurface, by a mould.
 21. The process of claim 17, wherein the mouldcarrying the film is a frame open at its center.
 22. The process ofclaim 17, wherein the film coated with the scratch-resistant layer ofelements constituting this layer is combined, before shaping, with oneor more other films which themselves fulfill functions or carry meansfor carrying out these functions other than the scratch-resistancefunction.
 23. A glass-free motor vehicle window, which is at leastpartly transparent, and which meets French standard R43 for motorvehicle windows, which comprises: a.) a plastic layer having a thicknessof 5 to 10 mm, b.) at least one skin layer of a plastic film having athickness of 10 to 100 μm coated on said plastic layer, at least oneadhesion layer between said layer a.) and layer b.), c.) ascratch-resistant layer having a thickness of 1 to 10 μm supported bysaid plastic film, wherein said scratch-resistant layer c.) isessentially inorganic or consists essentially of networks of entangledinorganic and organic molecular chains linked to each other bysilicon-carbon bonds.
 24. The glass-free motor vehicle window accordingto claim 23, wherein said scratch-resistant layer c.) consistsessentially of networks of entangled inorganic and organic molecularchains linked to each other by silicon-carbon bonds.
 25. The glass-freemotor vehicle window according to claim 24, wherein said networks ofentangled inorganic and organic molecular chains linked to each other bysilicon-carbon bonds are provided by an Ormocer varnish.